Plants (1-)2-5(-10) cm, dense or open mats. Stems green or yellow-green, usually brownish with age; stems of two types, fertile stems erect, branching distally or not, dendroid or not, sterile stems plagiotropic or arching, rarely erect, to 20 cm; rhizoids brown, macronemata mainly proximal, occasionally along underside of sterile stems, micronemata present. Leaves green or yellow-green, rarely black with age, variously crisped or contorted when dry, erect-spreading, usually flat, occasionally irregularly wavy or transversely undulate when moist, elliptic, obovate, oblong, oblong-lingulate, oblong-elliptic, or rarely orbicular or diamond-shaped, 1-14 mm; base decurrent or not; margins plane, green or yellow-green, 1-stratose, toothed, often to near base, sometimes only distally, rarely entire, teeth single, sharp or blunt, of 1-2(-4) cells, rarely hooked; apex acute, acuminate, obtuse, rounded, truncate, retuse, or emarginate, mucronate, apiculate, or cuspidate, cusp toothed or not, rarely bent to one side; costa percurrent, excurrent, or rarely subpercurrent, distal abaxial surface smooth; medial laminal cells short-elongate, elongate, or ± isodiametric, (15-)30-70(-85) µm, sometimes in diagonal or longitudinal rows, collenchymatous or not, walls pitted or not; marginal cells differentiated, linear or rhomboidal, in 2-4(-5) rows. Specialized asexual reproduction usually absent (by stolonlike stems in P. undulatum). Sexual condition synoicous or dioicous. Seta single or multiple, yellow, yellow-green, brown, sometimes reddish or greenish, rarely orange, dark red, or blackish with age, 1.2-5 cm, straight to flexuose. Capsule horizontal to pendent, yellow or yellowish brown, cylindric, oblong, oblong-cylindric, obovoid, or ovoid, 1.5-5 mm; operculum conic-apiculate or rostrate; exostome yellow or brown; endostome yellow to yellowish brown. Spores 18-40 µm.
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